Free the Handle when it it closed

Add Loop#dispose to help get rid of GC errors
Add Loop#handles to support Loop#dispose
Run Loop#dispose on all specs
Add Loop#one_shot_timer as a private method called on Lopp#run

It also closes the timer after it has been fired
Implement Loop#inspect
Implement Handle#closed?
Fix specs for new behavior of closed Handles
Rubinius does not have T_ZOMBIE defined, nor its semantics
Add support for passing a block to Stream#write